Filtration is a common means for extracting solids from liquids, usually involving forcing a slurry or mixture of solids and liquids through filtering materials. A slurry is usually taken to mean a watery suspension or mixture of insoluble solids in a liquid. As used herein, the term will encompass mixtures or suspensions of solid materials comprising particulate matter, gels, sludges and the like, which are at least partially insoluble in a liquid component comprising water, liquid organic or inorganic materials, and mixtures thereof. As used herein, such slurries can contain solids in suspension, or tending to settle naturally with time. Normally the filtrate or liquid passes downward through the filter with the solids remaining on the filter for recovery.
In many industries, e.g., the mining, oils and chemicals, wood pulp and agricultural industries, unfiltered waste slurries of liquids and solids are impounded in dammed earthen areas or "settling ponds". A settling pond is taken to be any concave depression in the ground, lined or unlined, which is used to collect slurries of solids and liquids. Generally such slurries are collected in settling ponds for separation, disposal or other processing. It is desirable to minimize the area of these settling ponds, to maximize disposal rates of slurries, and eventually to reclaim the areas by means including landfills and the like. However, often these areas never dry nor solidify, since evaporation is slow, and the slurried or flocculated solids never settle sufficiently so that the liquids can be pumped off. Effective means for dewatering such settling ponds without removing the sediment or settled solids are thus desirable. Similarly, it is desirable to have effective means for separating the liquid from a contained slurry of solids and liquids in general.